Planar thermoelastic bend actuator ink jet printing mechanism

ABSTRACT

This patent describes a new form of ink jet printer which a planar thermoelastic bend actuator to eject ink from a nozzle chamber. The thermal actuator includes a lower planar surface constructed from a highly conductive material such as a semiconductor metal layer interconnected to an upper planar material constructed from an electrically resistive material such as Indium Tin Oxide (ITO), such that, upon passing a current between the planar surfaces, the thermal actuator is caused to bend towards the ink ejection port so as to thereby cause the ejection of ink from the ink ejection port. The actuator is attached to a substrate and further includes a stiff paddle portion which increases the degree of bending of the actuator near the point where it is attached to the substrate. Surfaces are further coated with a passivation material as required.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

US PATENT APPLICATION CROSS-REFERENCED (CLAIMING RIGHT OF AUSTRALIANPRIORITY FROM PROVISIONAL PATENT AUSTRALIAN PROVISIONAL DOCKET No.APPLICATION) No. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO798809/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO801409/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO799909/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO803009/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO801509/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO798909/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO801809/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO802409/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO850109/112,797 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071 ART32 PO802209/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823 ART38 PO802309/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051 ART43 PO797709/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059 ART46 PO849909/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055 ART50 PO798609/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752 ART53 PO802709/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758 ART57 PO939609/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792 ART60 PO939909/112,791 ART61 PO9400 09/112,790 ART62 PO9401 09/112,789 ART63 PO940209/112,788 ART64 PO9403 09/112,795 ART65 PO9405 09/112,749 ART66 PP095909/112,784 ART68 PP1397 09/112,783 ART69 PP2370 09/112,781 DOT01 PP237109/113,052 DOT02 PO8003 09/112,834 Fluid01 PO8005 09/113,103 Fluid02PO9404 09/113,101 Fluid03 PO8066 09/112,751 IJ01 PO8072 09/112,787 IJ02PO8040 09/112,802 IJ03 PO8071 09/112,803 IJ04 PO8047 09/113,097 IJ05PO8035 09/113,099 IJ06 PO8044 09/113,084 IJ07 PO8063 09/113,066 IJ08PO8057 09/112,778 IJ09 PO8056 09/112,779 IJ10 PO8069 09/113,077 IJ11PO8049 09/113,061 IJ12 PO8036 09/112,818 IJ13 PO8048 09/112,816 IJ14PO8070 09/112,772 IJ15 PO8067 09/112,819 IJ16 PO8001 09/112,815 IJ17PO8038 09/113,096 IJ18 PO8033 09/113,068 IJ19 PO8002 09/113,095 IJ20PO8068 09/112,808 IJ21 PO8062 09/112,809 IJ22 PO8034 09/112,780 IJ23PO8039 09/113,083 IJ24 PO8041 09/113,121 IJ25 PO8004 09/113,122 IJ26PO8037 09/112,793 IJ27 PO8043 09/112,794 IJ28 PO8042 09/113,128 IJ29PO8064 09/113,127 IJ30 PO9389 09/112,756 IJ31 PO9391 09/112,755 IJ32PP0888 09/112,754 IJ33 PP0891 09/112,811 IJ34 PP0890 09/112,812 IJ35PP0873 09/112,813 IJ36 PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38PP1398 09/112,765 IJ39 PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41PP3991 09/112,807 IJ42 PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44PP3983 09/112,821 IJ45 PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02PO7937 09/112,826 IJM03 PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05PO8065 09/113,111 IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08PO8078 09/113,123 IJM09 PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11PO7949 09/113,129 IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14PO8073 09/113,126 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17PO8079 09/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20PO7948 09/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23PO7941 09/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26PO8051 09/113,074 IJM27 PO8045 09/113,089 IJM28 PO7952 09/113,088 IJM29PO8046 09/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 09/113,100 MEMS02PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04 PO8010 09/113,064MEMS05 PO8011 09/113,082 MEMS06 PO7947 09/113,081 MEMS07 PO794409/113,080 MEMS09 PO7946 09/113,079 MEMS10 PO9393 09/113,065 MEMS11PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses a planar thermoelastic bend actuator ink jet printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques on ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220(1988).

Ink Jet printers themselves come in many different types. Theutilization of a continuous stream of ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet el al)

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilises a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode of operation of a piezoelectric crystal, Stemmein U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectricoperation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4,584,590 which discloses a shear mode type of piezoelectric transducerelement.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclosed ink jetprinting techniques that rely upon the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Printing devices utilizing the electro-thermal actuator are manufacturedby manufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

The present invention relates to ink jet printing and in particular,discloses a new form of ink jet printer which utilizes a planarthermoelastic bend actuator to eject ink from a nozzle chamber.

In accordance with a first aspect of the present invention an ink jetnozzle is provided comprising a nozzle chamber having an ink ejectionport in one wall of the chamber, an ink supply source interconnected tothe nozzle chamber and a thermal actuator activated to eject ink fromthe nozzle chamber via the ink ejection port. Further, the thermalactuator comprises a lower planar surface constructed from a highlyconductive material interconnected to an upper planar materialconstructed from an electrically resistive material such that uponpassing a current between the planar surface, the thermal actuator iscaused to bend towards the ink ejection port so as to thereby cause theejection of ink from the ink ejection port. The actuator is attached toa substrate and further includes a stiff paddle portion which increasesthe degree of bending of the actuator near the point where it isattached to the substrate. Preferably, the stiff paddle is formed ofsilicon nitride. Advantageously, the actuator further includes anexpansion coating having a high coefficient of thermal expansion on topof the upper planar surface so as to increase the amount of bending ofthe actuator. The expansion coating can comprise substantiallypolytetrafluoroethylene. Between the upper and lower planar surfacesthere is provided a gap, constructed through the utilization of asacrificial material which is deposited and subsequently etched away soas to leave the gap. Further, the upper planar surface includes aplurality of etchant holes provided to allow a more rapid etching of thesacrificial layer during construction. Advantageously, the upper planarsurface of the actuator comprises substantially Indium Tin Oxide (ITO)whereas the lower planar surface of the actuator comprises substantiallya metal layer. Both surfaces are further coated with a passivationmaterial as required. The ink jet nozzle construction can be formed on asilicon wafer utilizing micro-electro mechanical systems constructiontechniques.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is cross-sectional view, partly in section, of a single ink jetnozzle constructed in accordance with an embodiment of the presentinvention;

FIG. 2 is an exploded perspective view illustrating the construction ofa single ink jet nozzle in accordance with an embodiment of the presentinvention;

FIG. 3 provides a legend of the materials indicated in FIGS. 4 to 19;and

FIG. 4 to FIG. 19 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, there is provided an ink jet printer havingnozzle chambers. Each nozzle chamber includes a thermoelastic bendactuator that utilizes a planar resistive material in the constructionof the bend actuator. The bend actuator is activated when it is requiredto eject ink from a chamber.

Turning now to FIG. 1, there is illustrated a cross-sectional view,partly in section of a nozzle arrangement 10 as constructed inaccordance with the preferred embodiment. The nozzle arrangement 10 canbe formed as part of an array of nozzles fabricated on a semi-conductorwafer utilizing techniques known in the production ofmicro-electro-mechanical systems (MEMS). For a general introduction to amicro-electric mechanical system (MEMS) reference is made to standardproceedings in this field including the proceedings of the SPIE(International Society for Optical Engineering), volumes 2642 and 2882which contain the proceedings for recent advances and conferences inthis field. The nozzle arrangement 10 includes a boron doped siliconwafer layer 12 which can be constructed by a back etching a siliconwafer 18 which has a buried boron doped epitaxial layer. The boron dopedlayer can be further etched so as to define a nozzle hole 13 and rim 14.

The nozzle arrangement 10 includes a nozzle chamber 16 which can beconstructed by utilization of an anisotropic crystallographic etch ofthe silicon portions 18 of the wafer.

On top of the silicon portions 18 is included a glass layer 20 which cancomprise CMOS drive circuitry including a two level metal layer (notshown) so as to provide control and drive circuitry for the thermalactuator. On top of the CMOS glass layer 20 is provided a nitride layer21 which includes side portions 22 which act to passivate lower layersfrom etching that is utilized in construction of the nozzle arrangement10. The nozzle arrangement 10 includes a paddle actuator 24 which isconstructed on a nitride base 25 which acts to form a rigid paddle forthe overall actuator 24. Next, an aluminium layer 27 is provided withthe aluminium layer 27 being interconnected by vias 28 with the lowerCMOS circuitry so as to form a first portion of a circuit. The aluminiumlayer 27 is interconnected at a point 30 to an Indium Tin Oxide (ITO)layer 29 which provides for resistive heating on demand. The ITO layer29 includes a number of etch holes 31 for allowing the etching away of alower level sacrificial layer which is formed between the layers 27, 29.The ITO layer is further connected to the lower glass CMOS circuitrylayer by via 32. On top of the ITO layer 29 is optionally provided apolytetrafluoroethylene layer (not shown) which provides for insulationand further rapid expansion of the top layer 29 upon heating as a resultof passing a current through the bottom layer 27 and ITO layer 29.

The back surface of the nozzle arrangement 10 is placed in an inkreservoir so as to allow ink to flow into nozzle chamber 16. When it isdesired to eject a drop of ink, a current is passed through thealuminium layer 27 and ITO layer 29. The aluminium layer 27 provides avery low resistance path to the current whereas the ITO layer 29provides a high resistance path to the current. Each of the layers 27,29 are passivated by means of coating by a thin nitride layer (notshown) so as to insulate and passivate the layers from the surroundingink. Upon heating of the ITO layer 29 and optionally PTFE layer, the topof the actuator 24 expands more rapidly than the bottom portions of theactuator 24. This results in a rapid bending of the actuator 24,particularly around the point 35 due to the utilization of the rigidnitride paddle arrangement 25. This accentuates the downward movement ofthe actuator 24 which results in the ejection of ink from ink ejectionnozzle 13.

Between the two layers 27, 29 is provided a gap 60 which can beconstructed via utilization of etching of sacrificial layers so as todissolve away sacrificial material between the two layers. Hence, inoperation ink is allowed to enter this area and thereby provides afurther cooling of the lower surface of the actuator 24 so as to assistin accentuating the bending. Upon de-activation of the actuator 24, itreturns to its quiescent position above the nozzle chamber 16. Thenozzle chamber 16 refills due to the surface tension of the ink throughthe gaps between the actuator 24 and the nozzle chamber 16.

The PTFE layer has a high coefficient of thermal expansion and thereforefurther assists in accentuating any bending of the actuator 24.Therefore, in order to eject ink from the nozzle chamber 16, a currentis passed through the planar layers 27, 29 resulting in resistiveheating of the top layer 29 which further results in a general bendingdown of the actuator 24 resulting in the ejection of ink.

The nozzle arrangement 10 is mounted on a second silicon chip waferwhich defines an ink reservoir channel to the back of the nozzlearrangement 10 for resupply of ink.

Turning now to FIG. 2, there is illustrated an exploded perspective viewillustrating the various layers of a nozzle arrangement 10. Thearrangement 10 can, as noted previously, be constructed from backetching to the boron doped layer. The actuator 24 can further beconstructed through the utilization of a sacrificial layer filling thenozzle chamber 16 and the depositing of the various layers 25, 27, 29and optional PTFE layer before sacrificially etching the nozzle chamber16 in addition to the sacrificial material in area 60. To this end, thenitride layer 21 includes side portions 22 which act to passivate theportions of the lower glass layer 20 which would otherwise be attackedas a result of sacrificial etching.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer deposit 3 microns of epitaxialsilicon heavily doped with boron 12.

2. Deposit 10 microns of epitaxial silicon 18, either p-type or n-type,depending upon the CMOS process used.

3. Complete a 0.5 micron, one poly, 2 metal CMOS process 20. This stepis shown in FIG. 4. For clarity, these diagrams may not be to scale, andmay not represent a cross section though any single plane of the nozzle.FIG. 3 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

4. Etch the CMOS oxide layers down to silicon 18 or second level metalusing Mask 1. This mask defines the nozzle cavity and the bend actuatorelectrode contact vias 28, 32. This step is shown in FIG. 5.

5. Crystallographically etch the exposed silicon 18 using KOH as shownat 40. This etch stops on <111> crystallographic planes 61, and on theboron doped silicon buried layer 12. This step is shown in FIG. 6.

6. Deposit 0.5 microns of low stress PECVD silicon nitride 41 (Si3N4).The nitride 41 acts as an ion diffusion barrier. This step is shown inFIG. 7.

7. Deposit a thick sacrificial layer 42 (e.g. low stress glass), fillingthe nozzle cavity. Planarize the sacrificial layer 42 down to thenitride 41 surface. This step is shown in FIG. 8.

8. Deposit 1 micron of tantalum 43. This layer acts as a stiffener forthe bend actuator.

9. Etch the tantalum 43 using Mask 2. This step is shown in FIG. 9. Thismask defines the space around the stiffener section of the bendactuator, and the electrode contact vias.

10. Etch nitride 41 still using Mask 2. This clears the nitride from theelectrode contact vias 28, 32. This step is shown in FIG. 10.

11. Deposit one micron of gold 44, patterned using Mask 3. This may bedeposited in a lift-off process. Gold is used for its corrosionresistance and low Young's modulus. This mask defines the lowerconductor of the bend actuator. This step is shown in FIG. 11.

12. Deposit 1 micron of thermal blanket 45. This material should be anon-conductive material with a very low Young's modulus and a lowthermal conductivity, such as an elastomer or foamed polymer.

13. Pattern the thermal blanket 45 using Mask 4. This mask defines thecontacts between the upper and lower conductors, and the upper conductorand the drive circuitry. This step is shown in FIG. 12.

14. Deposit 1 micron of a material 46 with a very high resistivity (butstill conductive), a high Young's modulus, a low heat capacity, and ahigh coefficient of thermal expansion. A material such as indium tinoxide (ITO) may be used, depending upon the dimensions of the bendactuator.

15. Pattern the ITO 46 using Mask 5. This mask defines the upperconductor of the bend actuator. This step is shown in FIG. 13.

16. Deposit a further 1 micron of thermal blanket 47.

17. Pattern the thermal blanket 47 using Mask 6. This mask defines thebend actuator, and allows ink to flow around the actuator into thenozzle cavity. This step is shown in FIG. 14.

18. Mount the wafer on a glass blank 48 and back-etch the wafer usingKOH, with no mask. This etch thins the wafer and stops at the buriedboron doped silicon layer 12. This step is shown in FIG. 15.

19. Plasma back-etch the boron doped silicon layer 12 to a depth of 1micron using Mask 7. This mask defines the nozzle rim 14. This step isshown in FIG. 16.

20. Plasma back-etch through the boron doped layer 12 using Mask 8. Thismask defines the nozzle 13, and the edge of the chips.

21. Plasma back-etch nitride 41 up to the glass sacrificial layer 42through the holes in the boron doped silicon layer 12. At this stage,the chips are separate, but are still mounted on the glass blank. Thisstep is shown in FIG. 17.

22. Strip the adhesive layer to detach the chips from the glass blank48.

23. Etch the sacrificial glass layer 42 in buffered HF. This step isshown in FIG. 18.

24. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply different colorsof ink to the appropriate regions of the front surface of the wafer.

25. Connect the printheads to their interconnect systems.

26. Hydrophobize the front surface of the printheads.

27. Fill the completed printheads with ink and test them. A fillednozzle is shown in FIG. 19.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the preferred embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademarkof the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow though inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 above which matches the docket numbers in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal Largeforce High power Canon Bubblejet bubble heater heats the ink togenerated Ink carrier 1979 Endo et al GB above boiling point, Simplelimited to water patent 2,007,162 transferring significant constructionLow efficiency Xerox heater-in- heat to the aqueous No moving parts Highpit 1990 Hawkins et ink. A bubble Fast operation temperatures al USP4,899,181 nucleates and quickly Small chip area required Hewlett-Packardforms, expelling the required for actuator High mechanical TIJ 1982Vaught et ink. stress al USP 4,490,728 The efficiency of the Unusualprocess is low, with materials required typically less than Large drive0.05% of the electrical transistors energy being Cavitation causestransformed into actuator failure kinetic energy of the Kogation reducesdrop. bubble formation Large print heads are difficult to fabricatePiezo- A piezoelectric crystal Low power Very large area Kyser et al USPelectric such as lead consumption required for actuator 3,946,398lanthanum zirconate Many ink types Difficult to Zoltan USP (PZT) iselectrically can be used integrate with 3,683,212 activated, and eitherFast operation electronics 1973 Stemme expands, shears, or Highefficiency High voltage USP 3,747,120 bends to apply drive transistorsEpson Stylus pressure to the ink, required Tektronix ejecting drops.Full pagewidth IJ04 print heads impractical due to actuator sizeRequires electrical poling in high field strengths during manufactureElectro- An electric field is Low power Low maximum Seiko Epson,strictive used to activate consumption strain (approx. Usui et al JPelectrostriction in Many ink types 0.01%) 253401/96 relaxor materialssuch can be used Large area IJ04 as lead lanthanum Low thermal requiredfor actuator zirconate titanate expansion due to low strain (PLZT) orlead Electric field Response speed magnesium niobate strength requiredis marginal (˜10 (PMN). (approx. 3.5 V/μm) μs) can be generated Highvoltage without difficulty drive transistors Does not require requiredelectrical poling Full pagewidth print heads impractical due to actuatorsize Ferro- An electric field is Low power Difficult to IJ04 electricused to induce a phase consumption integrate with transition between theMany ink types electronics antiferroelectric (AFE) can be used Unusualand ferroelectric (FE) Fast operation materials such as phase.Perovskite (<1 μs) PLZSnT are materials such as tin Relatively highrequired modified lead longitudinal strain Actuators require lanthanumzirconate High efficiency a large area titanate (PLZSnT) Electric fieldexhibit large strains of strength of around 3 up to 1% associated V/μmcan be readily with the AFE to FE provided phase transition. Electro-Conductive plates are Low power Difficult to IJ02, IJ04 static platesseparated by a consumption operate electrostatic compressible or fluidMany ink types devices in an dielectric (usually air). can be usedaqueous Upon application of a Fast operation environment voltage, theplates The electrostatic attract each other and actuator will displaceink, causing normally need to be drop ejection. The separated from theconductive plates may ink be in a comb or Very large area honeycombstructure, required to achieve or stacked to increase high forces thesurface area and High voltage therefore the force. drive transistors maybe required Full pagewidth print heads are not competitive due toactuator size Electro- A strong electric field Low current High voltage1989 Saito et al, static pull is applied to the ink, consumptionrequired USP 4,799,068 on ink whereupon Low temperature May be damaged1989 Miura et al, electrostatic attraction by sparks due to air USP4,810,954 accelerates the ink breakdown Tone-jet towards the printRequired field medium. strength increases as the drop size decreasesHigh voltage drive transistors required Electrostatic field attractsdust Permanent An electromagnet Low power Complex IJ07, IJ10 magnetdirectly attracts a consumption fabrication electro- permanent magnet,Many ink types Permanent magnetic displacing ink and can be usedmagnetic material causing drop ejection. Fast operation such asNeodymium Rare earth magnets High efficiency Iron Boron (NdFeB) with afield strength Easy extension required. around 1 Tesla can be fromsingle nozzles High local used. Examples are: to pagewidth printcurrents required Samarium Cobalt heads Copper (SaCo) and magneticmetalization should materials in the be used for long neodymium ironboron electromigration family (NdFeB, lifetime and low NdDyFeBNb,resistivity NdDyFeB, etc) Pigmented inks are usually infeasibleOperating temperature limited to the Curie temperature (around 540 K)Soft A solenoid induced a Low power Complex IJ01, IJ05, IJ08, magneticmagnetic field in a soft consumption fabrication IJ10, IJ12, IJ14, coreelectro- magnetic core or yoke Many ink types Materials not IJ15, IJ17magnetic fabricated from a can be used usually present in a ferrousmaterial such Fast operation CMOS fab such as as electroplated iron Highefficiency NiFe, CoNiFe, or alloys such as CoNiFe Easy extension CoFeare required [1], CoFe, or NiFe from single nozzles High local alloys.Typically, the to pagewidth print currents required soft magneticmaterial heads Copper is in two parts, which metalization should arenormally held be used for long apart by a spring. electromigration Whenthe solenoid is lifetime and low actuated, the two parts resistivityattract, displacing the Electroplating is ink. required High saturationflux density is required (2.0-2.1 T is achievable with CoNiFe [1])Lorenz The Lorenz force Low power Force acts as a IJ06, IJ11, IJ13,force acting on a current consumption twisting motion IJ16 carrying wirein a Many ink types Typically, only a magnetic field is can be usedquarter of the utilized. Fast operation solenoid length This allows theHigh efficiency provides force in a magnetic field to be Easy extensionuseful direction supplied externally to from single nozzles High localthe print head, for to pagewidth print currents required example withrare heads Copper earth permanent metalization should magnets. be usedfor long Only the current electromigration carrying wire need belifetime and low fabricated on the print- resistivity head, simplifyingPigmented inks materials are usually requirements. infeasible Magneto-The actuator uses the Many ink types Force acts as a Fischenbeck,striction giant magnetostrictive can be used twisting motion USP4,032,929 effect of materials Fast operation Unusual IJ25 such asTerfenol-D (an Easy extension materials such as alloy of terbium, fromsingle nozzles Terfenol-D are dysprosium and iron to pagewidth printrequired developed at the Naval heads High local Ordnance Laboratory,High force is currents required hence Ter-Fe-NOL). available Copper Forbest efficiency, the metalization should actuator should be pre- be usedfor long stressed to approx. 8 electromigration MPa. lifetime and lowresistivity Pre-stressing may be required Surface Ink under positive Lowpower Requires Silverbrook, EP tension pressure is held in a consumptionsupplementary force 0771 658 A2 and reduction nozzle by surface Simpleto effect drop related patent tension. The surface constructionseparation applications tension of the ink is No unusual Requiresspecial reduced below the materials required in ink surfactants bubblethreshold, fabrication Speed may be causing the ink to High efficiencylimited by surfactant egress from the Easy extension properties nozzle.from single nozzles to pagewidth print heads Viscosity The ink viscosityis Simple Requires Silverbrook, EP reduction locally reduced toconstruction supplementary force 0771 658 A2 and select which drops areNo unusual to effect drop related patent to be ejected. A materialsrequired in separation applications viscosity reduction can fabricationRequires special be achieved Easy extension ink viscosityelectrothermally with from single nozzles properties most inks, butspecial to pagewidth print High speed is inks can be engineered headsdifficult to achieve for a 100:1 viscosity Requires reduction.oscillating ink pressure A high temperature difference (typically 80degrees) is required Acoustic An acoustic wave is Can operate Complexdrive 1993 Hadimioglu generated and without a nozzle circuitry et al,EUP 550,192 focussed upon the plate Complex 1993 Elrod et al, dropejection region. fabrication EUP 572,220 Low efficiency Poor control ofdrop position Poor control of drop volume Thermo- An actuator which Lowpower Efficient aqueous IJ03, IJ09, IJ17, elastic bend relies upondifferential consumption operation requires a IJ18, IJ19, IJ20, actuatorthermal expansion Many ink types thermal insulator on IJ21, IJ22, IJ23,upon Joule heating is can be used the hot side IJ24, IJ27, IJ28, used.Simple planar Corrosion IJ29, IJ30, IJ31, fabrication prevention can beIJ32, IJ33, IJ34, Small chip area difficult IJ35, IJ36, IJ37, requiredfor each Pigmented inks IJ38, IJ39, IJ40, actuator may be infeasible,IJ41 Fast operation as pigment particles High efficiency may jam thebend CMOS actuator compatible voltages and currents Standard MEMSprocesses can be used Easy extension from single nozzles to pagewidthprint heads High CTE A material with a very High force can Requiresspecial IJ09, IJ17, IJ18, thermo- high coefficient of be generatedmaterial (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermal expansion Threemethods of Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as PTFEdeposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conductive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape Low voltageHigh current The shape change operation operation causes ejection of aRequires pre- drop. stressing to distort the martensitic state LinearLinear magnetic Linear Magnetic Requires unusual IJ12 Magnetic actuatorsinclude the actuators can be semiconductor Actuator Linear Inductionconstructed with materials such as Actuator (LIA), Linear high thrust,long soft magnetic alloys Permanent Magnet travel, and high (e.g.CoNiFe) Synchronous Actuator efficiency using Some varieties (LPMSA),Linear planar also require Reluctance semiconductor permanent magneticSynchronous Actuator fabrication materials such as (LRSA), Lineartechniques Neodymium iron Switched Reluctance Long actuator boron(NdFeB) Actuator (LSRA), and travel is available Requires the LinearStepper Medium force is complex multi- Actuator (LSA). available phasedrive circuitry Low voltage High current operation operation BASICOPERATION MODE Actuator This is the simplest Simple operation Droprepetition Thermal ink jet directly mode of operation: the No externalrate is usually Piezoelectric ink pushes ink actuator directly fieldsrequired limited to around 10 jet supplies sufficient Satellite dropskHz. However, this IJ01, IJ02, IJ03, kinetic energy to expel can beavoided if is not fundamental IJ04, 1305, IJ06, the drop. The drop dropvelocity is less to the method, but is IJ07, IJ09, IJ11, must have asufficient than 4 mls related to the refill IJ12, IJ14, IJ16, velocityto overcome Can be efficient, method normally IJ20, IJ22, IJ23, thesurface tension. depending upon the used IJ24, IJ25, IJ26, actuator usedAll of the drop IJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32,be provided by the IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38,Satellite drops IJ39, IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44velocity is greater than 4.5 mls Proximity The drops to be Very simpleprint Requires close Silverbrook, EP printed are selected by headfabrication can proximity between 0771 658 A2 and some manner (e.g. beused the print head and related patent thermally induced The drop theprint media or applications surface tension selection means transferroller reduction of does not need to May require two pressurized ink).provide the energy print heads printing Selected drops are required toseparate alternate rows of the separated from the ink the drop from theimage in the nozzle by nozzle Monolithic color contact with the printprint heads are medium or a transfer difficult roller.

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesElectro- The drops to be Very simple print Requires very Silverbrook, EPstatic pull printed are selected by head fabrication can highelectrostatic 0771 658 A2 and on ink some manner (e.g. be used fieldrelated patent thermally induced The drop Electrostatic fieldapplications surface tension selection means for small nozzle Tone-Jetreduction of does not need to sizes is above air pressurized ink).provide the energy breakdown Selected drops are required to separateElectrostatic field separated from the ink the drop from the may attractdust in the nozzle by a nozzle strong electric field. Magnetic The dropsto be Very simple print Requires Silverbrook, EP pull on ink printed areselected by head fabrication can magnetic ink 0771 658 A2 and somemanner (e.g. be used Ink colors other related patent thermally inducedThe drop than black are applications surface tension selection meansdifficult reduction of does not need to Requires very pressurized ink).provide the energy high magnetic fields Selected drops are required toseparate separated from the ink the drop from the in the nozzle by anozzle strong magnetic field acting on the magnetic ink. Shutter Theactuator moves a High speed (>50 Moving parts are IJ13, IJ17, IJ21shutter to block ink kHz) operation can required flow to the nozzle. Thebe achieved due to Requires ink ink pressure is pulsed reduced refilltime pressure modulator at a multiple of the Drop timing can Frictionand wear drop ejection be very accurate must be considered frequency.The actuator Stiction is energy can be very possible low Shuttered Theactuator moves a Actuators with Moving parts are IJ08, IJ15, IJ18, grillshutter to block ink Small travel can be required IJ19 flow through agrill to used Requires ink the nozzle. The shutter Actuators withpressure modulator movement need only small force can be Friction andwear be equal to the width used must be considered of the grill holesHigh speed (>50 Stiction is kHz) operation can possible be achievedPulsed A pulsed magnetic Extremely low Requires an IJ10 magnetic fieldattracts an ‘ink energy operation is external pulsed pull on ink pusher’at the drop possible magnetic field pusher ejection frequency. An Noheat Requires special actuator controls a dissipation materials for bothcatch, which prevents problems the actuator and the the ink pusher fromink pusher moving when a drop is Complex not to be ejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, osciliator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimul- actuator selects which operating speed phase and amplitude IJ08,IJ13, IJ15, ation) drops are to be fired The actuators must be carefullyIJ17, IJ18, IJ19, by selectively may operate with controlled IJ21blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 M and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. inkjet Any of the IJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium. drops is near or applications above air Tone-Jet breakdownDirect A magnetic field is Low power Requires Silverbrook, EP magneticused to accelerate Simple print head magnetic ink 0771 658 A2 and fieldselected drops of construction Requires strong related patent magneticink towards magnetic field applications the print medium. Cross Theprint head is Does not require Requires external IJ06, IJ16 magneticplaced in a constant magnetic materials magnet field magnetic field. Theto be integrated in Current densities Lorenz force in a the print headmay be high, current carrying wire manufacturing resulting in is used tomove the process electromigration actuator. problems Pulsed A pulsedmagnetic Very low power Complex print IJ10 magnetic field is used tooperation is possible head construction field cyclically attract a Smallprint head Magnetic paddle, which pushes size materials required in onthe ink. A small print head actuator moves a catch, which selectivelyprevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,1327, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric inkjetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can be used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418- into a high travel, Generally high 423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High energy is Hewlett-Packard expansion actuatorchanges, construction in the typically required to Thermal Inkjetpushing the ink in all case of thermal ink achieve volume CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal inkjet implementations Linear, Theactuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal toa direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14chip surface the print head surface. drops ejected required to achieveThe nozzle is typically normal to the perpendicular in the line ofsurface motion movement. Parallel to The actuator moves Suitable forFabrication IJ12, IJ13, IJ15, chip surface parallel to the print planarfabrication complexity IJ33, IJ34, IJ35, head surface. Drop FrictionIJ36 ejection may still be Stiction normal to the surface. Membrane Anactuator with a The effective Fabrication 1982 Howkins push high forcebut small area of the actuator complexity USP 4,459,601 area is used topush a becomes the Actuator size stiff membrane that is membrane areaDifficulty of in contact with the ink. integration in a VLSI processRotary The actuator causes Rotary levers Device IJ05, IJ08, IJ13, therotation of some may be used to complexity IJ28 element, such a grill orincrease travel May have impeller Small chip area friction at a pivotrequirements point Bend The actuator bends A very small Requires the1970 Kyser et al when energized. This change in actuator to be made USP3,946,398 may be due to dimensions can be from at least two 1973 Stemmedifferential thermal converted to a large distinct layers, or to USP3,747,120 expansion, motion. have a thermal IJ03, IJ09, IJ10,piezoelectric difference across the IJ19, IJ23, IJ24, expansion,actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33, IJ34, otherform of relative IJ35 dimensional change. Swivel The actuator swivelsAllows operation Inefficient IJ06 around a central pivot. where the netlinear coupling to the ink This motion is suitable force on the paddlemotion where there are is zero opposite forces Small chip area appliedto opposite requirements sides of the paddle, e.g. Lorenz force.Straighten The actuator is Can he used with Requires careful IJ26, IJ32normally bent, and shape memory balance of stresses straightens whenalloys where the to ensure that the energized. austenic phase isquiescent bend is planar accurate Double The actuator bends in Oneactuator can Difficult to make IJ36, IJ37, IJ38 bend one direction whenbe used to power the drops ejected by one element is two nozzles. bothbend directions energized, and bends Reduced chip identical. the otherway when size. A small another element is Not sensitive to efficiencyloss energized. ambient temperature compared to equivalent single bendactuators. Shear Energizing the Can increase the Not readily 1985Fishbeck actuator causes a shear effective travel of applicable to otherUSP 4,584,590 motion in the actuator piezoelectric actuator material.actuators mechanisms Radial con- The actuator squeezes Relatively easyHigh force 1970 Zoltan USP striction an ink reservoir, to fabricatesingle required 3,683,212 forcing ink from a nozzles from glassInefficient constricted nozzle. tubing as Difficult to macroscopicintegrate with VLSI structures processes Coil/uncoil A coiled actuatorEasy to fabricate Difficult to IJ17, IJ21, IJ34, uncoils or coils moreas a planar VLSI fabricate for non- IJ35 tightly. The motion of processplanar devices the free end of the Small area Poor out-of-plane actuatorejects the ink. required, therefore stiffness low cost Bow The actuatorbows (or Can increase the Maximum travel IJ16, IJ18, IJ27 buckles) inthe middle speed of travel is constrained when energized. MechanicallyHigh force rigid required Push-Pull Two actuators control The structureis Not readily IJ18 a shutter. One actuator pinned at both ends,suitable for ink jets pulls the shutter, and so has a high out-of- whichdirectly push the other pushes it. plane rigidity the ink Curl A set ofactuators curl Good fluid flow Design IJ20, IJ42 inwards inwards toreduce the to the region behind complexity volume of ink that theactuator they enclose. increases efficiency Curl A set of actuators curlRelatively simple Relatively large IJ43 outwards outwards, pressurizingconstruction chip area ink in a chamber surrounding the actuators, andexpelling ink from a nozzle in the chamber. Iris Multiple vanes encloseHigh efficiency High fabrication IJ22 a volume of ink. These Small chiparea complexity simultaneously rotate, Not suitable for reducing thevolume pigmented inks between the vanes. Acoustic The actuator vibratesThe actuator can Large area 1993 Hadimioglu vibration at a highfrequency. be physically distant required for et al, EUP 550,192 fromthe ink efficient operation 1993 Elrod et al, at useful frequencies EUP572,220 Acoustic coupling and crosstalk Complex drive circuitry Poorcontrol of drop volume and position None In various inkjet No movingparts Various other Silverbrook, EP designs the actuator tradeoffs are0771 658 A2 and does not move. required to related patent eliminatemoving applications parts Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkrefilled. After the Operational force relatively jet actuator isenergized, simplicity small compared to IJ01-IJ07, IJ10- it typicallyreturns actuator force IJ14, IJ16, IJ20, rapidly to its normal Longrefill time IJ22-IJ45 position. This rapid usually dominates returnsucks in air the total repetition through the nozzle rate opening. Theink surface tension at the nozzle then exerts a small force restoringthe meniscus to a minimum area. This force refills the nozzle. ShutteredInk to the nozzle High speed Requires IJ08, IJ13, IJ15, oscillatingchamber is provided at Low actuator common ink IJ17, IJ18, IJ19, inkpressure a pressure that energy, as the pressure oscillator IJ21oscillates at twice the actuator need only May not be drop ejection openor close the suitable for frequency. When a shutter, instead ofpigmented inks drop is to be ejected, ejecting the ink drop the shutteris opened for 3 half cycles: drop ejection, actuator return, and refill.The shutter is then closed to prevent the nozzle chamber emptying duringthe next negative pressure cycle. Refill After the main High speed, asRequires two IJ09 actuator actuator has ejected a the nozzle isindependent drop a second (refill) actively refilled actuators pernozzle actuator is energized. The refill actuator pushes ink into thenozzle chamber. The refill actuator returns slowly, to prevent itsreturn from emptying the chamber again. Positive ink The ink is held aslight High refill rate, Surface spill Silverbrook, EP pressure positivepressure. therefore a high must be prevented 0771 658 A2 and After theink drop is drop repetition rate Highly related patent ejected, thenozzle is possible hydrophobic print applications chamber fills quicklyhead surfaces are Alternative for:, as surface tension and requiredIJ01-IJ07, ink pressure both IJ10-IJ14, IJ16, operate to refill theIJ20, IJ22-IJ45 nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill Thermal inkjet channel to the nozzle chamberOperational rate Piezoelectric ink is made long and simplicity Mayresult in a jet relatively narrow, Reduces relatively large chip IJ42,IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01- pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22, IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the inkjet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, IJ05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, 1139, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofinkjet, there is no problem is inkback-flow on 0771 658 A2 and does notexpansion or eliminated actuation related patent result in ink movementof an applications back-flow actuator which may Valve-jet cause inkback-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most inkjet nozzlefiring fired periodically, complexity on the sufficient to systemsbefore the ink has a print head displace dried ink IJ01, IJ02, IJ03,chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09,IJ10, are seated (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20,IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26,IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, afterIJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to acleaning IJ39, IJ40, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra Insystems which heat Can be highly Requires higher Silverbrook, EP powerto the ink, but do not boil effective if the drive voltage for 0771 658A2 and ink beater it under normal heater is adjacent to clearing relatedpatent situations, nozzle the nozzle May require applications clearingcan be larger drive achieved by over- transistors powering the heaterand boiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used succession rapid succession. In extradrive circuits depends with: IJ01, IJ02, of actuator someconfigurations, on the print head substantially upon IJ03, IJ04, IJ05,pulses this may cause heat Can be readily the configuration of IJ06,IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzleIJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20,IJ22, clearing the nozzle. In logic IJ23, IJ24, 1325, other situations,it may IJ27, IJ28, IJ29, cause sufficient IJ30, IJ31, IJ32, vibrationsto dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, 1338, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Notsuitable May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable bard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle HighIJ08, IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EPclearing plate is pushed against severely clogged mechanical 0771 658 A2and plate the nozzles. The plate nozzles alignment is related patent hasa post for every required applications nozzle. A post moves Moving partsare through each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required.

Description Advantages Disadvantages Examples NOZZLE PLATE CONSTRUCTIONElectro- A nozzle plate is Fabrication High Hewlett Packard formedseparately fabricated simplicity temperatures and Thermal Ink jet nickelfrom electroformed pressures are nickel, and bonded to required to bondthe print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., USP lowcost head 5,208,604 May produce thin burrs at exit holes Silicon Aseparate nozzle High accuracy is Two part K. Bean, IEEE micro- plate isattainable construction Transactions on machined micromachined from Highcost Electron Devices, single crystal silicon, Requires Vol. ED-25, No.10, and bonded to the precision alignment 1978, pp 1185-1195 print headwafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins et al., USP4,899,181 Glass Fine glass capillaries No expensive Very small 1970Zoltan USP capillaries are drawn from glass equipment required nozzlesizes are 3,683,212 tubing. This method Simple to make difficult to formhas been used for single nozzles Not suited for making individual massproduction nozzles, but is difficult to use for bulk manufacturing ofprint heads with thousands of nozzles. Monolithic, The nozzle plate isHigh accuracy Requires Silverbrook, EP surface deposited as a layer (<1μm) sacrificial layer 0771 658 A2 and micro- using standard VLSIMonolithic under the nozzle related patent machined depositiontechniques. Low cost plate to form the applications using VLSI Nozzlesare etched in Existing nozzle chamber IJ01, IJ02, IJ04, litho- thenozzle plate using processes can be Surface may be IJ11, 1312, 1317,graphic VLSI lithography and used fragile to the touch IJ18, IJ20, IJ22,processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34,IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, Thenozzle plate is a High accuracy Requires long IJ03, IJ05, IJ06, etchedburied etch stop in the (<1 μm) etch times IJ07, IJ08, IJ09, throughwafer. Nozzle Monolithic Requires a IJ10, IJ13, IJ14, substrate chambersare etched in Low cost support wafer IJ15, IJ16, IJ19, the front of thewafer, No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26thinned from the back side. Nozzles are then etched in the etch stoplayer. No nozzle Various methods have No nozzles to Difficult to Ricoh1995 plate been tried to eliminate become clogged control drop Sekiya etal USP the nozzles entirely, to position accurately 5,412,413 preventnozzle Crosstalk 1993 Hadimioglu clogging. These problems et al EUP550,192 include thermal bubble 1993 Elrod et al mechanisms and EUP572,220 acoustic lens mechanisms Trough Each drop ejector has ReducedDrop firing IJ35 a trough through manufacturing direction is sensitivewhich a paddle moves. complexity to wicking. There is no nozzleMonolithic plate. Nozzle slit The elimination of No nozzles to Difficultto 1989 Saito et al instead of nozzle holes and become clogged controldrop USP 4,799,068 individual replacement by a slit position accuratelynozzles encompassing many Crosstalk actuator positions problems reducesnozzle clogging, but increases crosstalk due to ink surface waves DROPEJECTION DIRECTION Edge Ink flow is along the Simple Nozzles limitedCanon Bubblejet (‘edge surface of the chip, construction to edge 1979Endo et al GB shooter’) and ink drops are No silicon High resolutionpatent 2,007,162 ejected from the chip etching required is difficultXerox heater-in- edge. Good heat Fast color pit 1990 Hawkins et sinkingvia substrate printing requires al USP 4,899, 181 Mechanically one printhead per Tone-jet strong color Ease of chip handing

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesSurface Ink flow is along the No bulk silicon Maximum inkHewlett-Packard (‘roof surface of the chip, etching required flow isseverely TJJ 1982 Vaught et shooter’) and ink drops are Silicon can makerestricted al USP 4,490,728 ejected from the chip an effective heatIJ02, IJ11, IJ12, surface, normal to the sink IJ20, IJ22 plane of thechip. Mechanical strength Through Ink flow is through the High ink flowRequires bulk Silverbrook, EP chip, chip, and ink drops are Suitable forsilicon etching 0771 658 A2 and forward ejected from the front pagewidthprint related patent (‘up surface of the chip. heads applicationsshooter’) High nozzle IJ04, IJ17, IJ18, packing density IJ24, IJ27-IJ45therefore low manufacturing cost Through Ink flow is through the Highink flow Requires wafer IJ01, IJ03, IJ05, chip, chip, and ink drops areSuitable for thinning 1306, IJ07, IJ08, reverse ejected from the rearpagewidth print Requires special IJ09, IJ10, IJ13, (‘down surface of thechip. heads handling during IJ14, IJ15, IJ16, shooter’) High nozzlemanufacture IJ19, IJ21, IJ23, packing density IJ25, IJ26 therefore lowmanufacturing cost Through Ink flow is through the Suitable forPagewidth print Epson Stylus actuator actuator, which is notpiezoelectric print heads require Tektronix hot fabricated as part ofheads several thousand melt piezoelectric the same substrate asconnections to drive ink jets the drive transistors. circuits Cannot bemanufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleed on paper All IJ series ink humectant, and May jets biocide.strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ121, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks are mediumcan be used Printed pages USP 4,820,346 usually wax based, No papercockle may ‘block’ All IJ series ink with a melting point occurs Inktemperature jets around 80° C. After No wicking may be above the jettingthe ink freezes occurs curie point of almost instantly upon No bleedoccurs permanent magnets contacting the print No strikethrough Inkheaters medium or a transfer occurs consume power roller. Long warm-uptime Oil Oil based inks are High solubility High viscosity: All IJseries ink extensively used in medium for some this is a significantjets offset printing. They dyes limitation for use in have advantages inDoes not cockle ink jets, which improved paper usually require acharacteristics on Does not wick low viscosity. Some paper (especiallyno through paper short chain and wicking or cockle). multi-branched oilsOil soluble dies and have a sufficiently pigments are required. lowviscosity. Slow drying Micro- A microemulsion is a Stops ink bleedViscosity higher All IJ series ink emulsion stable, self forming Highdye than water jets emulsion of oil, water, solubility Cost is slightlyand surfactant. The Water, oil, and higher than water characteristicdrop size amphiphilic soluble based ink is less than 100 nm, dies can beused High surfactant and is determined by Can stabilize concentrationthe preferred curvature pigment required (around of the surfactantsuspensions 5%)

What is claimed is:
 1. An ink jet printhead comprising: a nozzle chamberhaving an ink ejection port in one wall of said chamber; an ink supplysource interconnected to said nozzle chamber; and a thermal actuatoractivated to eject ink from said nozzle chamber via said ink ejectionport, said thermal actuator comprising a lower planar surfaceconstructed from a highly electrically conductive materialinterconnected to an upper planar material constructed from anelectrically resistive material such that upon passing a current betweensaid planar surfaces, said thermal actuator is caused to bend towardssaid ink ejection port so as to thereby cause to be ejected ink fromsaid ink ejection port.
 2. An ink jet printhead as claimed in claim 1wherein said actuator is attached to a substrate and further includes astiff paddle portion which increases bending of said actuator near thepoint where it is attached to the substrate.
 3. An ink jet printhead asclaimed in claim 2 wherein said stiff paddle is formed of siliconnitride.
 4. An ink jet printhead as claimed in claim 1 wherein saidactuator further includes an expansion coating having a high coefficientof thermal expansion on top of said upper planar surface so as toincrease bending of said actuator.
 5. An ink jet printhead as claimed inclaim 4 wherein said expansion coating comprises substantiallypolytetrafluoroethylene.
 6. An ink jet printhead as claimed in claim 1wherein between said upper planar surface and said lower planar surfacethere is provided a gap, constructed through utilization of asacrificial material which is deposited and subsequently etched away soas to leave said gap.
 7. An ink jet printhead as claimed in claim 6wherein said upper planar surface includes a plurality of etchant holesprovided so as to allow a more rapid etching of said sacrificial layerduring construction.
 8. An ink jet printhead as claimed in claim 1wherein said upper planar surface comprises substantially Indium TinOxide (ITO).
 9. An ink jet printhead as claimed in claim 1 wherein saidlower planar surface comprises substantially a metal layer.
 10. An inkjet nozzle as claimed in claim 1 wherein said surfaces are furthercoated with a passivation material as required.
 11. An ink jet printheadas claimed in claim 1 wherein said ink jet printhead is formed on asilicon wafer utilising micro-electro mechanical systems constructiontechniques.